Energy Production In Lipids Flashcards
True or false: lipids are hydrophilic
False - they’re hydrophobic
Are lipids soluble in water?
No
True or False: Lipids are more reduced than carbohydrates
True. This means they release more energy when oxidised
True or false: complete oxidation of lipids requires more oxygen than carbohydrates
True - lipids are more reduced than carbohydrates
Give 3 examples of fatty acids derivatives
- fatty acids
- Triacylglycerols
- Phospholipids
Give 3 examples of Hydroxy-methyl-glutaric acid derivatives
- Ketone bodies
- Cholesterol
- Bile acids and salts
Give 4 examples of lipid soluble vitamins
A, D, E and K
What are fatty acids stored as
Triacylglycerols
Where do you get lipid soluble vitamins from
Diet
What are triacylglycerols made up of
3 carbon glycerol backbone and 3 fatty acid side chains
What process produces triacylglycerols
Esterification
What process breaks down triacylglycerols
Lipolysis
Are triacylglycerols hydrophobic or hydrophilic
Hydrophobic
Where are triacylglycerols stored
Adipose tissue
How are triacylglycerols stored?
In an anhydrous form of lipid droplets
What hormone mobilises fat
Glucagon
What hormone causes the storage of fat
Insulin
What are chylomicrons
Lipoprotein particles that transport triglycerides in the blood via the lymphatics to adipose tissue
What hydrolyses lipids in the pancreas
Pancreatic lipases
How are fatty acids transported from storage in adipose tissue to consumer tissue
Albumin fatty acids complexes
What happens to fatty acids in consumer tissues
Oxidised to produce energy
In which cells does metabolism of fatty acids not occur
- RBC as they have no mitochondria
2. Brain as fatty acids cant pass through the blood brain barrier
What does a low glucose level do to fatty acids stores in adipose tissue
Releases it to be used as an alternative fuel
What does it mean if fats are saturated and unsaturated
- saturated = no double bonds
- unsaturated = one or more double bonds
What does amphipathic mean
Contains both hydrophobic and hydrophilic groups
Why are some polyunsaturated fatty acids essential
Mammals cant make a double bond beyond carbon 9
Where does fatty acid metabolism occur
Mitochondria
How are fatty acids activated in their metabolism
By linking them to coenzyme A outside the mitochondria
What transports the activated fatty acids across the inner mitochondrial membrane
Carnitine shuttle
What enzyme activates fatty acids
Fatty acyl CoA synthase
True or false: activated fatty acids can cross the inner mitochondrial membrane readily
False - this is why they require the carintine shuttle transporter
Is ATP needed for fatty acid activation
Yes
What is the activated fatty acid called
Fatty acylCoA
Why can the activated fatty acid complex cross the outer mitochondrial membrane but not the inner one
The inner mitochondrial membrane is impermeable
How does the carnitine shuttle transport work
The activated fatty acid complex exchanges the CoA for carnitine using the enzyme carnitine acyltransferase. This complex can then pass through the transport via facilitated diffusion and then returns back to the CoA complex once inside
What enzyme is used in the carnitine shuttle transport
Carnitine acyltransferase
What is the carnitine shuttle transporter inhibited by
Malonyl CoA
What can defects in the carnitine shuttle transporter cause
Exercise Intolerance and lipid droplets in muscle
What happens to the fatty acid CoA complex once it enters the intermitochondrial space
The fatty acid goes through a series of oxidation steps with 2 carbons removed in each cycle
What is the end product of beta-oxidation
Acetyl CoA
Does beta-oxidation occur in the absence of oxygen
No
How many moles of atp are produced in the beta oxidation pathway
None
Where is glycerol metabolised
Liver
Outline glycerol metabolism
- Glycerol is converted into glycerol phosphate using atp
- glycerol phosphate is then either used in triacylglycerol synthesis or produces dihydroxyacetone phosphate which can be used in glycolysis.
What enzyme is used to convert glycerol into glycerol phosphate
Glycerol kinase
What is CoA derived from
B vitamins
Where are ketone bodies produced
Liver
Give 3 examples of ketone bodies
- Acetoacetate
- Acetone
- Beta- hydroxybutyrate
How is acetone produced
Spontaneous (non-enzymatic) decarboxylation of acetoacetate
What is normal plasma ketone levels
Less than 1 mM
Outline the production of ketone bodies
Acetyl CoA is converted into Hydroxymethy glutaryl-CoA by synthase which then is converted into ketone bodies by lyase
What enzyme converts acetyl CoA into Hydroxymethy glutaryl-CoA
Synthase
What enzyme converts Hydroxymethy glutaryl-CoA into ketone bodies
Lyase
What do statin drugs do
Inhibits the production of cholesterol by inhibiting the action of HMG-CoA reductase
When is acetyl CoA used to make ketone bodies instead of entering the Kreb’s cycle
Beta oxidation causes high NADH production which inhibits the enzymes in the Kreb’s cycle meaning acetyl CoA cant enter the Kreb’s cycle
How are ketone bodies metabolised
They are oxidised to reform acetyl CoA when then enters the Kreb’s cycle
What determines whether ketone bodies or cholesterol will be produced from hydroxymethyl glutaryl CoA
- in high insulin lyase is inhibited so cholesterol is produced
- in high glucagon (starvation) reductase is inhibited so keton bodies are produced
What enzymes are used to produce cholesterol
HMG reductase
What does the production of ketone bodies in starvation do to the glucose
Spares it so that it is only used by the brain (conserves glucose)
What is ketogenesis
The production of ketone bodies from fatty acids
What happens in prolonged starvation
Protein is broken down to amino acids which is converted in to Pyruvate in the liver and then into glucose by gluconeogensis
What is it called when the ketone leave is above the threshold and excreted in urine
Ketonuria
What is ketoacidosis
A build up of ketone bodies in the blood as they are acidic
How might volatile acetone be excreted
In the lung and so you can smell it on their breath
